The invention relates to a rotary tablet press with a die plate rotatably mounted in a housing.
Such tablet presses comprises a so-called die plate with die bores with which the upper and lower punch cooperate, these being guided in the die plate. The movement of the upper and lower punch are to some extent controlled by cams. Corresponding plates or rings are arranged rigid with the housing below or above the die plate whilst the die plate is rotatably mounted and is drivable by an upright shaft arranged there below. For reasons of cleaning or the exchange of the punch it is from time to time necessary the re-equip the machine. From EP 0 288 798 it is known to provide the cams with retainers which can be connected to stationary housing parts by way of releasable connecting means. Via lugs the cams are connected to the die plate such that after a releasing of the connecting means the die plate together with the upper and lower punch and the cams may be lifted off the drive shaft. With the help of a carrier aim or likewise which is laterally traversed in, the whole assembly may be moved laterally out of the machine.
With such rotary presses the actual actuation of the upper and lower punch is effected via so-called pressing rollers which where appropriate are mounted in a bearing which is rigid with the housing. For the removal of the described die plate assembly it is also necessary to either adjust or disassemble the pressing rollers so that the described removal of the die plate assembly may take place. From EP 0 460 295 it is also known to mount the pressing rollers in a bearing block which with a receiving flange is displaceably held in a guide of a housing by the drive for the pressing roller in the radial direction to the rotational axis of the die plate. The bearing block is releasably connected to the housing of the drive.
As mentioned, the die plate is set into rotation by a drive shaft which is rotatably mounted in the machine housing below the die plate and is driven by a suitable drive. The connection between the parts is effected preferably by way of a suitable screwing. Before the removal of the die plate this screwing is therefore to be released. Inversely the screwing after the renewed placing-on of the die plate must be actuated in order to connect the parts to one another. This procedure is relatively complex, not least because the access to the screw locations is difficult.
It is therefore the object of the invention to provide a rotary tablet press, with which the connection between the die plate and drive shaft may be quickly made and released.
This object is achieved by the features of the present invention.
With the tablet press according to the invention at the ends, facing one another, of the die plate and drive shaft there is provided a quick lock whose parts are arranged on cavities of the die plate and the drive shaft. The actuation of the quick lock is effected via an actuation rod which is movably mounted in an axial channel of the drive shaft and is actuatable by an actuation device for the selective tensioning and releasing of the lug plate and drive shaft.
The quick lock envisages movably mounted means which selectively may be brought into engagement with locking or tensioning surfaces of the lug plate in order to rotationally rigidly couple the lug plate to the drive shaft. For this reason the described means are arranged in the cavity of the drive shaft but however project from the cavity beyond the end of the drive shaft and engage into the facing cavity of the die plate, in order to selectively lock or release this. The actuation of these means is effected via an actuation rod in the hollow lug shaft wherein the actuation rod is however preferably mounted axially movable in order to actuate the quick lock. The actuation of the actuation rod must be effected from outside the drive shaft, wherein for this a separate drive is provided. Alternatively also an actuation by hand is conceivable.
Various designs for the quick lock and the type of rotational coupling are conceivable. According to the invention one envisages that the drive shaft and the die plate comprise annular lug surface which may bear against one another and which may be tensioned against one another with the help of the quick lock. It is conceivable the bring the lug surfaces into engagement with one another with a positive fit, i.e. to form these similar to a claw. They may however also be smooth when an adequate pressing force is produced for the friction transmission of the rotating force.
Furthermore in the cavity of the matrix disk and/or the drive shaft there may be provided a clamping surface, for example a conical angular surface which may be selectively brought into engagement with a clamping element actuated by the actuation rod. On actuation of the clamping element this engages the clamping surface and pulls the die plate disk and drive shaft against one another.
The actuation of the clamping element according to a further formation of the invention is effected preferably with the help of a tensioning cone which is connected to the axially movable actuation rod. The tensioning cone cooperates with one cone surface with an actuation surface of the tensioning element, so that this element for its part with the tensioning surface mainly cooperates with the die plate. Preferably there are provided a multitude of claw-like tensioning elements uniformly distributed in the circumferential direction, which are pivotable mounted about an axis approximately perpendicular to the axis of the drive shaft in the cavity of the drive shaft.
The tensioning cone may, according to a further formation of the invention, comprise a conical bracing surface at an axial distance to the tensioning cone surface, this bracing surface cooperating with a conical actuation surface on the tensioning element in a mauler such that the tensioning element is moved in the release position when the bracing surface is brought into engagement with the actuation surface. This formation is an alternative to a possible spring impingement of the tensioning element in a manner such that it is biased into the release position.
It is conceivable in the cavity of the die plate and the drive shaft by way of suitable shaping machining to manufacture tensioning surfaces. Preferably however a separate tensioning ring is provided which is mounted in the cavity, preferably in that it is screwed into the cavity, as a result has a thread on the outer side.
If several tensioning elements are provided, then these according to one formation of the invention may not only be pivotable but also radially movable in a limited maimer. If the tensioning elements are provided with oppositely aligned conical tensioning surfaces and the die plate and drive shaft in each case have one tensioning surface, wherein the angles of the tensioning surfaces are likewise oppositely aligned, it is then possible by radial adjustment of the tensioning element to create an axial force between the two parts to be tensioned. In order to effect a pivoting mounting of the tensioning elements, according to one formation of the invention these have radial outer lying bearing projections which cooperate with the bearing ring which cooperates with a shoulder of the cavity of the drive shaft. The bearing ring, which preferably is formed of plastic, may comprise bearing chambers limited by radial webs, in which the bearing projections of the tensioning elements are accommodated.
According to a further formation of the invention the drive shaft comprises a centering ring which surrounds the upper part of the drive shaft and projects upwardly beyond the lug surface. Its inner diameter is dimensioned in a manner such that an end section of an axial cylindrical collar of the die plate may fittingly engage into the centering ring.
Various possibilities are conceivable to adjust the actuation rod at a distance to the quick lock. According to the invention one envisages that the rod comprises an adjusting thread at a distance to the free upper end, in which a spindle nut is seated. The spindle nut in a suitable maimer is axially secured in the channel of the drive shaft. A rotational drive laterally of the drive shaft comprises an adjusting wheel which via an opening in the drive shaft cooperates with the spindle nut. The spindle nut may therefore on the outside comprise a toothing and the adjusting wheel a complementary toothing in order to effect a rotation of the nut. Since the spindle nut of the actuation rod is only effected temporarily during a change or removal or installation of the die plate, the rotational drive is adjustably mounted in order during the normal operation of the drive shaft to bring the adjusting wheel outside the operating region of the drive shaft.